首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   83484篇
  免费   559篇
  国内免费   428篇
化学   27374篇
晶体学   843篇
力学   6946篇
数学   33119篇
物理学   16189篇
  2023年   52篇
  2022年   139篇
  2021年   159篇
  2020年   166篇
  2019年   183篇
  2018年   10538篇
  2017年   10339篇
  2016年   6246篇
  2015年   1004篇
  2014年   526篇
  2013年   698篇
  2012年   4149篇
  2011年   10867篇
  2010年   5836篇
  2009年   6258篇
  2008年   6888篇
  2007年   8983篇
  2006年   437篇
  2005年   1498篇
  2004年   1701篇
  2003年   2104篇
  2002年   1145篇
  2001年   358篇
  2000年   381篇
  1999年   207篇
  1998年   234篇
  1997年   188篇
  1996年   266篇
  1995年   166篇
  1994年   130篇
  1993年   160篇
  1992年   107篇
  1991年   121篇
  1990年   99篇
  1989年   96篇
  1988年   95篇
  1987年   104篇
  1986年   113篇
  1985年   94篇
  1984年   95篇
  1983年   73篇
  1982年   87篇
  1981年   75篇
  1980年   78篇
  1979年   92篇
  1978年   70篇
  1977年   58篇
  1976年   51篇
  1973年   47篇
  1914年   45篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs.  相似文献   
2.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
3.

A Savitzky–Golay filtering for smoothing and peak search written in Python is presented in this paper alongside its applications in the list-mode digital data acquisition dual gamma–gamma coincidence bismuth germanate (BGO) detector. The study has demonstrated that the software provides a reliable and effective way to quantify trace amounts of 22Na and 7Be in aerosol samples collected at Resolute Bay, Canada with a critical limit of 3 mBq and 5 Bq respectively for a 20 h counting interval, which are believed to be the inherent limitations of the dual-BGO system.

  相似文献   
4.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
5.
6.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
7.
8.
9.
10.
Journal of Thermal Analysis and Calorimetry - In this study, the efficacy of incorporating phase change material (PCM) into the building walls on the annual heat transfer reduction is examined....  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号